Large Ring Research Articles

Size Distribution of Emission Vortex Rings in Turbulence Induced by Vibrating Wire in Superfluid $$^4$$He

We report the spontaneous emission of vortex rings from turbulence induced by a vibrating wire in superfluid $$^4$$ He, and investigate the statistical behavior of quantum turbulence. Using a set of vibrating wires as a turbulence generator and vortex detectors, we measured the distribution of times of flights between the generator and the detectors for emission directions parallel and perpendicular to the vibration direction of the generator wire. We find that the times exhibit a single exponential distribution for emissions in both directions, indicating temporally random emission of vortex rings with a single mean emission rate. When a limit is set on the detection diameter of the vortex rings, the detection times exhibit a double exponential distribution for the perpendicular direction for ring diameters above 10 $$\upmu \hbox {m}$$ , suggesting that large vortex rings reach the detector with a high rate emission at later times. In the parallel emission direction, the emission rate during an equilibrium state exhibits a power law behavior with a minimum diameter of detected vortex rings, implying that a vortex tangle generated by an oscillating object has a self-similar structure of vortex lines.

Intermolecular channel expansion induced by cation-π interactions to enhance lithium storage in a crosslinked π-conjugated organic anode

The design and synthesis of novel π-conjugated polymers receive tremendous attention in electrochemical energy storage. We report a lithium-doped crosslinked π-conjugated polymer, PTAT@LiCl, with excellent electrochemical performance as an anode material for lithium ion batteries (LIBs). Benefiting from a wider range of intermolecular channel caused by cation-π interaction inducing lithium ion insert into polymer network, the prepared PTAT@LiCl shows high capacity (892 mAh g−1, 100 mA g−1), excellent rate performance (200 mAh g−1, 4C), and outstanding cycle life (500 cycles). This work provides a new insight into the performance enhancement of organic LIBs through noncovalent cation-π (Li+-π) interaction between lithium ions and large π-conjugated aromatic ring, which are meaningful for the potential application of LIBs.

Molecular mechanism of the expansion of silica glass upon exposure to moisture

AbstractMolecular dynamics simulations show that the expansion of silica glass occurs by the presence of the hydroxyl (SiOH) groups present in the glass as opposed to intact water (H2O) molecules, providing an accurate molecular description of the experimentally observed volume changes in silica glass exposed to water. Using a robust and accurate reactive potential, the simulations show that the expansion is caused by the rupture of siloxane (Si–O–Si) linkages in the glass via reactions with water molecules, forming SiOHs. Such reactions remove smaller rings and form larger rings, with a decrease in the overall number of rings smaller than a prescribed large ring size in comparison to dry glasses. This change in ring structure overcomes the inherently stronger hydrogen bonding in the glasses containing SiOH in comparison to the glasses containing predominantly intact H2O molecules. This stronger H‐bonding of the SiOH also causes a shift to lower frequencies in the high‐frequency OH vibrational spectrum for the silanols, as shown in previous ab‐initio calculations. This introduces a question about assuming the lower frequency part of the high‐frequency peak is only due to intact H2O molecules. A slight decrease in volume occurred in the glasses containing the largest concentration of intact H2O molecules. There is no change in the ring size distribution between the H2O glasses and dry glasses. Rather, the slight decrease in volume in the H2O system is caused by a decrease in siloxane bond angles caused by the formation of H‐bonds between the H2O molecules and the glass O in the siloxane cages surrounding the H2O molecules.

Photonic crystal terahertz wave logic AND-XOR gate

Terahertz wave logic gates are one of the key devices required in terahertz wave communication systems and signal processing systems. In this paper, we design a logic gate to realize the function of AND gate and XOR gate. The logic AND-XOR gate is based on two large photonic crystal ring resonators, one small ring resonator and photonic crystal branch waveguides. The structure is analyzed and simulated by treating the plane wave expansion and finite difference time domain methods. The steady-state field distributions and output power characteristics of the gate are analyzed. The simulation results show that the designed device with the feasibility can be used in terahertz wave integrated digital circuit.

Geological Position and Structural Control of Ore Mineralization in the Toupugol–Khanmeishor District (the Polar Urals) Based on the Remote Sensing Results

Large ring, arc, and radial structures have been identified by complex processing of the multispectral satellite imagery of the Landsat. These structures control the gold mineralization position in the Toupugol–Khanmeishor ore district (Novogodnenskoe ore cluster, Polar Urals). This area has been compared with the Tur’insk–Auerbakh ore district (Auerbakh ore cluster, Northern Urals). Similar geological features, regularity in the structures, and the location of gold mineralization in the system of morphostructures have been revealed. The formation depth of the magmatic chambers has been determined for the Novogodnenskoe and Auerbakh paleovolcanic structures for the first time. These chambers are located at depths of ~4 and ~20 km, respectively, in the upper and middle parts of the earth’s crust. The Novogodnenskoe structure is a monogenic structure. It was formed under the influence of one leading geological process. The Auerbakh structure is a larger and more complex structure; it is characterized by a long and multistage development. According to the paleovolcanic reconstruction results, the root (focal) part of the Auerbakh structure plunged from the southeast to the northwest during the evolution of the magmatic process. Gold mineralization within the studied areas of the Northern Urals is confined to the intersections of radial faults near the centers of large concentric morphostructures.

A metal\u2013peptide capsule by multiple ring threading

Cavity creation is a key to the origin of biological functions. Small cavities such as enzyme pockets are created simply through liner peptide folding. Nature can create much larger cavities by threading and entangling large peptide rings, as learned from gigantic virus capsids, where not only chemical structures but the topology of threaded rings must be controlled. Although interlocked molecules are a topic of current interest, they have for decades been explored merely as elements of molecular machines, or as a synthetic challenge. No research has specifically targeted them for, and succesfully achieved, cavity creation. Here we report the emergence of a huge capsular framework via multiple threading of metal–peptide rings. Six equivalent C4-propeller-shaped rings, each consisting of four oligopeptides and Ag+, are threaded by each other a total of twelve times (crossing number: 24) to assemble into a well-defined 4 nm-sized sphere, which acts as a huge molecular capsule.

Study on soot evolution under different hydrogen addition conditions at high temperature by ReaxFF molecular dynamics

The physical and chemical properties evolution of soot particles was studied by ReaxFF MD simulation. The dimerization of PAHs, nucleation and coagulation, and graphitization from hydrocarbons to the final soot nanoparticle were investigated, and the chemical effects of the hydrogen addition on the formation mechanism of primary soot nanoparticle was explored by considering important polycyclic aromatic hydrocarbons (PAHs) in ethylene flames under high temperatures. The results obtained reveal that, in the first stage, the activated aliphatic hydrocarbons mainly grow into a large ring through the chain growth reactions, and then gradually form PAH-like molecules with inner ring bridging instead of directly generating the five or six-carbon ring structures. Hydrogenation effectively inhibited the soot nanoparticle nucleation at all stages. Due to a large number of vinyl and acryl groups attacked by the hydrogen to decarbonize and produce methane, a rapid decrease of the formation and growth rate of the PAHs was observed. With the increase of hydrogen, the nucleation and surface growth rate of soot particles are slowed down due to lose activity.

Mechanistic insights into the kinetic compensation effects during the gasification of biochar: Effects of the partial pressure of H2O

This study has focused on the kinetic compensation effects (KCE) during the gasification of biochar in 15% H2O-Ar and 2% H2O-Ar. The biochar samples were characterised by FT-Raman and X-ray photoelectron spectroscopies. We found that the extent of the KCE of char gasification and formation of CO, CO2, and H2 was higher during the gasification in 15% H2O-Ar than that in 2% H2O-Ar. The relative ratio of ID/(I(Gr+Vl+Vr) was higher in 15% H2O-Ar than that in 2% H2O-Ar, which reflects that the relative concentration of large aromatic rings is higher during the gasification in 15% H2O-Ar than that in 2% H2O-Ar. The partial pressure of H2O affected the relative concentration of O-containing surface species [C(O)] on the biochar external surface and inside the pores of the char matrix. The concentration of these O-containing species [C(O)] on the char surface led to different relative rates of CO and CO2 release, resulting in lower CO/CO2 ratios (at lower char conversions) during the gasification in 15% H2O-Ar than those in 2% H2O-Ar. The lower relative ratio of ID/(I(Gr+Vl+Vr) and lower extent of the kinetic compensation effects revealed that the relative concentration of active sites (with similar properties), which were created on the activation of aromatic rings, was lower for the gasification in 2% H2O-Ar than that in 15% H2O-Ar.

Electromagnetic strain measurements and two-directional mechanical stress estimation for a REBaCuO ring bulk reinforced by a metal ring during field-cooled magnetization

In this paper, simultaneous measurements of the electromagnetic strains along both the circumferential (θ) and radial (r) directions are reported for a large single-grain EuBaCuO ring bulk reinforced by an Al alloy ring during field-cooled magnetization (FCM) from 5 T at 50 K using several strain gauges adhered to the surface. To verify the experimental results and to understand the complex stress–strain behavior, mechanical analyses were carried out using a three-dimensional finite element model that closely represents the experimental setup. The simulation results of the electromagnetic strains along both directions showed excellent qualitative and quantitative agreement with the experimental ones. These results strongly suggest that the numerical model must include the exact same structure (size, shape and materials) of the mechanical support structure as the experimental setup in order to reproduce the experimental results both qualitatively as well as quantitatively. This also explains our previous research (SuST 2019 32 015007), where the measured circumferential strains were about 50% smaller those in the numerical simulation. Furthermore, the electromagnetic stresses along both directions during the FCM process are estimated from the obtained experimental strains. As a result, the estimated stresses were fairly consistent with those obtained by the numerical simulations, suggesting that our stress–strain simulation technique is both qualitatively and quantitatively reliable and useful to clarify the possibility of mechanical fracture of bulk superconductors.

Structural origin of the anomalous density maximum in silica and alkali silicate glasses

AbstractSilica, sharing the same tetrahedral order and many structural, thermodynamic and dynamic anomalies with water, has been speculated to have a density increase upon melting similar to water. In this work, an increase in density upon melting cristobalite silica and a shallow density maximum followed by a density minimum during cooling of silica liquid are observed in classical molecular dynamics simulations. The density maximum gradually diminishes with the increase in alkali size/content in alkali silicate glasses. The structural origin of the anomalous density maximum in silica is revealed by detailed structural analysis. During the cooling process, a range of rings with different sizes form in liquid silica, with 6‐member rings being the most dominant, which cause the silica network to open up and compensate the regular volume shrinkage upon cooling. These two competing factors lead to a density maximum, but to a less extent than that observed in melting of cristobalite silica. With the increase in modifier size/content in the alkali silicate glasses, the connectivity of silica network gradually breaks down; the population of 6‐member rings decrease with the increase in smaller or larger rings, therefore the density maximum becomes less obvious and eventually disappears.

Earth rotation variations observed by VLBI and the Wettzell “G” ring laser during the CONT17 campaign

Abstract. The VLBI (Very Long Baseline Interferometry) technique can provide the full set of parameters needed for the transformation between celestial and terrestrial reference frames with high accuracy. Yet it has some limitations regarding temporal resolution and continuity, and the accuracy of the resulting Earth Orientation Parameters (EOP) varies depending on the network geometry. In this work we explore the benefit of combining VLBI observations with the measurements of the large ring laser gyroscope “G” in Wettzell for deriving highly resolved ERP (Earth Rotation Parameters, i.e. polar motion and universal time variations, δUT1). We examine the observations collected by two simultaneously operating VLBI networks during the 15 d of the CONT17 campaign. These two networks, of 14 globally distributed telescopes each, were designed for the estimation of Earth rotation variations, for which reason the resulting hourly ERP are appointed as benchmark in this investigation. To evaluate the advantage of a VLBI and ring laser combined solution, we create degraded versions of the original networks, containing only six stations. The ERP derived from those sparse networks and from the VLBI sparse plus ring laser solutions are then compared in terms of differences to the reference values. It should certainly be considered that these are relative numbers, since they are also determined by the number and selection of the stations remaining in the sparse networks. The root mean square of the difference to the benchmark is reduced by 24 % in case of δUT1 from one network. The polar motion yp component from the same network moves 14 % closer to the reference value due to the inclusion of the ring laser data. The impact on xp and on all ERP from the other network ranges between 2 % and 9 %. The research again confirms the feasibility and also the potential gain of a combined evaluation of VLBI and ring laser observations, but the full capacity of such a sensor fusion will emerge once the ring laser gyroscopes reach a level of accuracy similar to VLBI.

Influence and compensation of CMM geometric errors on 3D gear measurements

The influence of CMM geometric errors on 3D gear measurements is still unclear as the requirement for a gear measurement standard with ideal geometry cannot be fulfilled. To solve this issue, the authors have proposed and developed a software program named Me2Ge to simulate 3D gear measurements with CMMs. This allows a systematic analysis of how gear deviations are affected by geometric errors of a CMM, and how the influence can be reduced. A large gear ring measurement standard and a large Cartesian CMM are used as an important application example. The simulation results achieve the gear deviations under the influence of machine geometric errors, and reveal the major error sources for profile slope deviation, helix slope deviation and single pitch deviation, which gives a first impression of geometric errors and their influence on 3D gear measurements. Finally, reversal techniques are integrated into the Me2Ge program to compensate machine errors. The results clearly prove that reversal techniques play a significant role and are worth spending the necessary time to achieve lower measurement uncertainties.

Amorphous iron formation following occupancy of iron atoms in vacant sites of epsilon-iron that transformed from alpha-iron during rubbing in a low vacuum

The main purpose of this paper is to present two TEM diffraction patterns taken from a layer (more than 100 μm thick) of piled-up adhered wear debris on a rubbed surface. The unidirectional rubbing was made in a low vacuum, regularly separating the slider from the specimen. The specimen and the slider were α-iron. One of the diffraction patterns consists of large spots and halo rings and the other consists of small faint spots and halo rings. The latter seems to be the state just before the perfect amorphization. All the spots in the diffraction patterns correspond to the structure formed due to the occupancy of iron atoms in O and T sites of ε-iron. Neither this way of amorphization nor the occupied structure mentioned above has not been reported. Both the amorphous state and the occupied structure remain at ambient conditions. The mechanism of high-pressure generation that transformed α-iron to ε-iron and the generation of high tensile stress that breaks the atomic bonds in wear debris are presented. The latter is considered to have enabled the occupancy.

Physicochemical Properties and AAEM Retention of Copyrolysis Char from Coal Blended with Corn Stalks

Physicochemical properties (i.e., morphological variation, functional groups, and carbon structure change) and alkali and alkaline earth metal retention of chars during coal and corn stalks (CS) copyrolysis were investigated in this research. The copyrolysis char samples were obtained at the temperature ranging from 400 to 1000 °C at intervals of 100 °C under argon atmosphere by a horizontal furnace. The results indicate that the synergistic effects on char yields are slight or even negligible. The presence of CS promotes the formation of plastic mass during copyrolysis because of the interactions between volatiles and chars of coal and CS. As the pyrolysis temperature increases from 400 to 1000 °C, the aromatic C–H functional groups first increase and then decrease, and the char structure changes from a small aromatic ring system to a large aromatic ring system containing six or more fused benzene rings. The average number of hydrogen atoms per aromatic ring and the number of the aromatic ring structure with high substitution degree are highest at 500 °C. In addition, the C═O and aliphatic C–H functional groups in the char samples disappear when the pyrolysis temperature ranges from 600 to 700 °C. The release of K and Mg is inhibited during copyrolysis, while the release of Ca is promoted.

Finite Element Method Linear Triangular Element for Solving Nanoscale InAs⁄GaAs Quantum Ring Structures

This paper concerned with the solution of the nanoscale structures consisting of the with an effective mass envelope function theory, the electronic states of the quantum ring are studied. In calculations, the effects due to the different effective masses of electrons in and out the rings are included. The energy levels of the electron are calculated in the different shapes of rings, i.e., that the inner radius of rings sensitively change the electronic states. The energy levels of the electron are not sensitively dependent on the outer radius for large rings. The structures of quantum rings are studied by the one electronic band Hamiltonian effective mass approximation, the energy- and position-dependent on electron effective mass approximation, and the spin-dependent on the Ben Daniel-Duke boundary conditions. In the description of the Hamiltonian matrix elements, the Finite elements method with different base linear triangular element is adopted. The non-linear energy confinement problem is solved approximately by using the Finite elements method with linear triangular element, to calculate the energy of the electron states for the quantum ring.

An 18-member carbon ring

Surface Chemistry Carbon's allotropes include molecular species such as C60 and C70 fullerenes. Kaiser et al. now report the assembly of a large carbon ring, cyclo[18]carbon, from organic precursors whose reactivity was controlled by adsorbing them on a sodium chloride surface at 5 kelvin (see the Perspective by Maier). Manipulation, with an atomic force microscope tip, of a cyclocarbon oxide molecule, C24O6, led to elimination of carbon monoxide molecules and formation of the desired all-carbon ring. High-resolution imaging revealed alternating single and triple bonds versus an all-double-bond structure. Science , this issue p. [1299][1]; see also p. [1245][2] [1]: /lookup/doi/10.1126/science.aay1914 [2]: /lookup/doi/10.1126/science.aay7461

Surface chemical properties and pore structure of the activated coke and their effects on the denitrification activity of selective catalytic reduction

In order to study the mechanism of selective catalytic reduction of activated coke to remove NO in low-temperature flue gas and provide some theoretical basis for the development of related technologies. The pore size distribution and BET specific surface area of AC were obtain by data analyzing of N2 adsorption/desorption isotherm at − 196 °C and carbon matrix and surface chemistry of virgin activated coke samples were characterized by acid–base titration and XPS. The process of selective catalytic reduction of activated coke (AC) samples with NH3 as reducing agent was studied in a fixed bed reactor at 150 °C. The result shows that pore size distribution or BET specific surface of activated cokes have not correlation with denitrification activity for SCR. The NO reduction activities of the activated cokes are apparent to increase with their surface oxygen element content and total amount of acidic sites. Obviously there is good linear relationship between the NH3 adsorption capacity and activity for SCR with linear correlation coefficient 0.943. It has been presented that adsorption of NH3 on acidic functional groups in the edge of large polycyclic aromatic ring of activated coke is key rate controlling step in the SCR heterogeneous catalytic reaction.

Predicting the sorption of azithromycin and levofloxacin to sediments from mineral and organic components

Despite the strong association of azithromycin (AZM), a macrolide antibiotic, and levofloxacin (LVF), a quinolone antibiotic, to sediment, sorption data are scarce. We conducted sorption experiments with eight river sediments, their major clay minerals (illite and chlorite), a highly negatively charged clay mineral (montmorillonite), and an organic-matter-rich soil (Andosol). The sorption of AZM and LVF to the sediments was influenced by the concentration and type of coexisting inorganic cations as much as by reported organic cations. In addition, their linear sorption coefficients (Kd) to sediments were correlated with cation exchange capacity (CEC) but not organic carbon content, so cation exchange is the dominant sorption mechanism. Multiple linear regression analysis showed improved prediction of sediment Kd from CEC contributed by minerals and organic matter for AZM, but not for LVF. Kcec (= Kd/CEC) values of AZM were 2–3 orders of magnitude higher on minerals than on Andosol, but those of LVF ranged within a factor of 4. Therefore, mineral and organic components need to be separated in estimating AZM sorption to sediments. Sediment Kd values of AZM and LVF were satisfactorily predicted by a cation-exchange-based model using individual Kcec values on illite, chlorite, and Andosol (mean absolute error of 0.57 and 0.22 log units, respectively). Kcec values on montmorillonite and chlorite ranged within a factor of about 3 from those of illite for both antibiotics, and Kcec differences by mineral type would generally be negligible in model estimation. Because AZM was sorbed mostly to minerals in sediments, the model and sorption data can be applicable to various soils or sediments. Overall, the trend of LVF sorption corresponds to reported sorption of other organic cations, whereas remarkably higher AZM Kcec to minerals than to Andosol is attributable to its large lactone ring, higher molecular weight, or two charged amines.

반경-축 방향 링 롤링 공정의 정의 및 제어를 위한 분석적인 접근법

This research aims to provide a useful algorithm for the prediction of the geometrical expansion of flat rings in the radialaxial ring rolling process in case of multiple variations of the mandrel feeding speed during the process. The proposed algorithm was subjected to a 2-phases validation process, where results were compared with those of laboratory experiments, conducted at 150℃ on rings made of AA-1070 and AA-6061 aluminum alloys, and with numerical simulations, considering 7 different rings with outer diameter ranging from 800 to 2000 ㎜ and made of 42CrMo4 steel alloy, Ti6Al4V titanium alloy and AA-6061 aluminum alloys. In the first and second validation phases, the maximum deviation in the estimation of the outer diameter of the ring has been calculated in 1.7% and 6.82%, respectively. According to the results of the validation, the proposed algorithm is able to properly predict the geometrical expansion of the ring for multiple variations of the mandrel feeding speed during the process and has good accordance with both relatively small and large rings.

Partial structure investigation of the traditional bulk metallic glass Pd40Ni40P20

Local structures of ${\mathrm{Pd}}_{40}{\mathrm{Ni}}_{40}{\mathrm{P}}_{20}$ bulk metallic glass were investigated by combining anomalous x-ray scattering close to the Pd and Ni $K$ absorption edges, x-ray diffraction, neutron diffraction, and reverse Monte Carlo modeling, from which partial structure factors ${S}_{ij}(Q)$ and partial pair distribution functions ${g}_{ij}(r)$ as well as three-dimensional atomic configurations were carefully obtained around the constituent elements. A disagreement is found in the local structures with an ab initio molecular dynamics simulation by Guan et al., i.e., the existence of the P-P nearest-neighboring configurations is clarified in the present experimental result. From the Voronoi tessellation analysis, a preference of the pure icosahedral configurations is observed around the Ni atoms, whereas the local configurations around the Pd and P atoms are rather distorted icosahedra. A persistent homology analysis was carried out to identify meaningful shape characteristics of the intermediate-range atomic configuration of large rings.